Clean energy? Mother Nature still knows best

As concerns about securing clean energy grow with the world at large, researchers continue their efforts to find the most abundant supply of energy available to us. Most experts have turned to sunlight to meet their objective. The challenge, however, is to determine how best to capture, transfer and store solar energy efficiently. Now an international team of researchers has discovered that the complex systems at work in nature could be the answer to this problem. Presented in the journal Nature Chemistry, their study puts the spotlight on natural antenna complexes. Their research was funded in part by the PHOTPROT ('The dynamic protein matrix in photosynthesis: from disorder to life') project, which has clinched a European Research Council (ERC) grant EUR 2.86 million under the EU's Seventh Framework Programme (FP7).

Following their assessment of studies probing natural sunlight-harvesting antenna complexes in plants and microorganisms, scientists in Canada, the Netherlands, the United Kingdom and the United States have compiled the information they found into a guide for researchers and engineers that design future solar energy technologies. By looking at natural photosynthesis, the team provides insight into how human-made molecular energy circuits can be developed to capture, regulate, amplify and direct raw solar energy.

With this information in hand, experts could effectively plug into the plentiful sunlight that is available, later convert and store its energy, and then transfer this power over many distances — all this is possible within the arrays of microscopic energy grids.

'More than 10 million billion photons of light strike a leaf each second,' the Digital Journal quoted Dr Greg Scholes, a chemist from the Department of Chemistry at the University of Toronto in Canada, as saying. 'Of these, almost every red-coloured photon is captured by chlorophyll pigments which feed plant growth.'

One of the challenges is to route the energy from sunlight that is captured and stored for only a billionth of a second by chromophores, what experts define as coloured dye or pigment molecules, before it is lost.

The researchers say that despite the fact that experts have been investigating photosynthesis for over a century, replicating the design principles involved in this complex natural process will be possible if changes are implemented in how existing chemical synthesis procedures are carried out. What is needed is novel approaches to mimic the way nature's chromophores are arranged and how natural molecular excitation energy is tuned to optimise light harvesting within solar antenna complexes in leaves and algae. They add that electronic excitation transport in nature is probably the biggest chemical dynamics challenge.

The results of their work can lead to a framework for the design and synthesis of working molecular-scale artificial photosynthesising antenna units and systems. Engineering artificial chromophores with large absorption capacity, arranging these pigment molecules in optimal patterns on the antennas and benefiting from the collective properties of the light-absorbing molecules are key, the researchers say.

'Solar energy is forecasted to provide a significant fraction of the world's energy needs over the next century, as sunlight is the most abundant source of energy we have at our disposal,' the Digital Journal quoted co-author Graham Fleming of the University of California, Berkeley in the United States as saying. 'However, to utilise solar energy harvested from sunlight efficiently we must understand and improve both the effective capture of photons and the transfer of electronic excitation energy.'